Stargazing - 06.07.12
The Big Dipper stands high in the north this evening.
Follow the line formed by the stars that form the outer edge of the bowl down toward the horizon to Polaris, the North Star.
Follow the curve of the dipper’s handle away from the bowl to bright yellow-orange Arcturus.
When astronomers talk about “windows” on the universe, they’re not talking about the kind that let in an afternoon breeze. Instead, they’re talking about slices of the electromagnetic spectrum — wavelengths of energy that reveal different details about the universe.
One of the last windows to open was the extreme ultraviolet — a type of energy produced by some of the hottest objects. The window was thrown open by a spacecraft that was launched 20 years ago today: EUVE — the Extreme Ultraviolet Explorer.
When the probe was launched, astronomers weren’t sure just what it would see, because gas and dust between the stars easily absorbs extreme-ultraviolet wavelengths. Instruments on other spacecraft had detected a few objects, but not many.
It turned out that EUVE could see the universe just fine. It cataloged more than 800 objects, including the cores of galaxies, the “dead” stars known as white dwarfs, and disks of hot gas around stars in binary systems — including some systems where one of the objects was a black hole.
The craft’s observations also showed that the gas and dust between the stars isn’t spread out evenly. There are big bubbles and gaps, giving the galaxy the texture of Swiss cheese. The bubbles were probably cleared out by exploding stars.
EUVE was shut down in January of 2001, and burned up when it plunged back into the atmosphere a year later — closing, for a while, a window on the “hot” universe.